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Monoscopic X-Ray Imaging for Real-Time Three-Dimensional Target Localization Using Multiple Internal Fiducial Markers

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N Miyamoto

N Miyamoto1*, R Suzuki1 , S Takao1, 2 , T Matsuura2, 3 , T Fujii4 , S Hirayama4 , H Koyano4 , S Shimizu2, 4 , K Umegaki2, 3 , H Shirato2, 4 , (1) Department of Medical Physics, Hokkaido University Hospital, Japan, (2) Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Japan, (3) Graduate School of Engineering, Hokkaido University, Japan, (4) Graduate School of Medicine, Hokkaido University, Japan


WE-RAM1-GePD-J(A)-5 (Wednesday, August 2, 2017) 9:30 AM - 10:00 AM Room: Joint Imaging-Therapy ePoster Lounge - A

Purpose: To evaluate the three-dimensional target localization accuracy of a proposed monoscopic X-ray imaging technique using the alignment of fiducial markers and motion data.

Methods: The proposed method utilizes three or more internal fiducial markers. The distance between markers must be known in advance and the imaging device must be calibrated to obtain the equation of the line connecting the X-ray source and the projected position of the marker on the detector. The three-dimensional marker position can be obtained by searching the markers on the connecting line satisfying the pre-defined distance. In this study, the three-dimensional measurement error of the fiducial marker was investigated by a simulation study using three fiducial markers’ position and motion trajectory gathered from 10 patients who underwent proton therapy for prostate cancer. Source to isocenter distance and source to detector distance were assumed to be 0.7 and 2.1 m, respectively in order to simulate with large magnification. Measurement error was defined as the root mean square error between the input position and the evaluated position of the marker.

Results: The measurement error depended on the axis of imaging coordinates. The error in the direction perpendicular to the imaging axis was less than 0.1 mm. The mean and standard deviation of measurement error in the imaging direction was 1.1 +/- 0.4 mm when the accuracy of marker registration in the X-ray image was assumed to be about 0.1 mm. A registration accuracy of 0.1 mm is achievable using template pattern matching with sub-pixel accuracy.

Conclusion: The results demonstrate the feasibility and suggest the proposed method can be applied for target localization with rigid alignment of multiple markers. Robustness to deformation of the marker layout will be assessed in future work to consider the application for lung or liver treatment.

Funding Support, Disclosures, and Conflict of Interest: This research was partially supported by Development of Medical Devices and Systems for Advanced Medical Services from Japan Agency for Medical Research and development, AMED.

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